1. Field of the Invention
The present invention relates to adhesive tapes for electronic parts to be used for adhering between parts around leadframes making up a semiconductor device, e.g., lead pins, semiconductor chip mounted substrates, heat spreader, semiconductors themselves.
2. Description of the Related Art
Conventionally, adhesive tapes for fixing a leadframe, TAB tapes, etc., are used as adhesive tapes for use in the interior of resin-molded type semiconductor devices. For example, the adhesive tapes for fixing a leadframe have been used to fix lead pins of the leadframe in order to enhance the efficiency for producing the leadframe itself and the whole semiconductor assembly stages. In general, a leadframe manufacturer tapes a leadframe, and brings it to a semiconductor manufacturer, at which a chip is mounted thereon followed by molding the leadframe with a resin. For this reason, it has been required for the adhesive tapes for fixing the leadframe not only to possess general reliability in a level required for semiconductor and enough processability at the time of taping, but also to possess sufficient adhesive strength immediately after taping and heat resistance enough for withstanding thermal process at the stages of assembling semiconductor devices.
Conventionally, the adhesive tapes for use in such an application include adhesive tapes applying on a support film of a polyimide film, etc., an adhesive comprising a synthetic rubber resin such as polyacrylonitrile, polyacrylate or acrylonitrile-butadiene copolymer solely, or modified with any other resin or blended with any other resin to come into a B-stage.
In recent years, resin-molded type semiconductor devices (semiconductor package) shown in FIG. 2 has been developed or produced. In FIG. 2, the device has a construction in which lead pins 3 and metal plane 2 are connected by means of an adhesive layer 6, a semiconductor chip 1 is mounted on the metal plane 2, and together with bonding wires 4 between the semiconductor chip 1 and the lead pins 3, they are molded with a resin 5.
In the adhesive layer in the resin-molded type semiconductor device shown in FIG. 2, the use of an adhesive tape to which a conventional adhesive is applied has the problems such as insufficient heat resistance. Also, in the case of the application of polyimide resin, the conditions of temperature and pressure for taping and conditions for curing are severe so that the metal material, such as leadframe, are damaged. Consequently, it has been desired to develop an adhesive for electronic parts which can be bonded and cured at a relatively low temperature, and which has sufficient heat resistance and reliability, etc.
The present inventors have proposed an adhesive tape using an ahdesive comprising a piperazinylethylamino-carbonyl-containing butadiene-acrylonitrile copolymer represented by the under-mentioned formula (I) and a compound having at least 2 maleimide groups (Japanese Patent Application Laid-Open 126591/1995), whereby the above problems are dissolved.
However, there are still problems in this adhesive tape when the semiconductor device shown in FIG. 2 is produced. In order to produce the semiconductor device shown in FIG. 2, a tape having an adhesive layer on each side thereof is used for fixing the leadframe and the metal plane. In this case, after the tape is cut by a mold in every 1 piece, the piece of the tape is laminated with the leadframe and the plane, and they are bonded by pressing under heat. This process requires much cost. Also, it is necessary to change the mold for cutting the tape when the design of the leadframe or the plane is changed.